1. Field of the Invention
The present invention relates to a workpiece heating and feeding device which can be used in wire bonders, die bonders or curing devices that are used in the manufacture of semiconductor devices.
2. Prior Art
Conventionally, workpiece heating and feeding devices used in bonders, for example, consist of three general types. The three types are (a) devices in which the area above the heating block that heats the workpieces (e.g. the lead frames, etc.) is open (as shown in FIG. 3), (b) devices in which the area above the heating block is closed (as shown in FIG. 4) or (c) devices in which the entire periphery of the heating block is sealed off (as shown in FIG. 5).
The device shown in FIG. 3 (wherein the area above the heating block is open) is the most common type of device used. In this device, a split lid 5 is fastened to guide rails 3 which guide the workpieces 1, so that the workpieces 1 will not float upward as they are fed by the feeding claws 4. In other words, nothing is installed above the central portions of the workpieces 1 portions of the workpieces are left exposed.
Such a device operates in the following manner. With the heating block 2 in a lowered position, the feeding claws 4 are caused to complete a cycle in which the claws 4 are lowered and, caused to complete a forward motion in the horizontal direction (perpendicular to the plane of the paper as shown in FIG. 3), raised and caused to complete a return motion in the horizontal direction. As a result of this cycle, the workpieces 1 are fed by one pitch. After the movement of the feeding claws 4 stops, the heating block 2 is raised, so that each workpiece is heated.
The device illustrated in FIG. 4 (wherein the area above the heating block is closed) is used in cases where the workpieces 1 or leads formed on the workpieces 1 consist of materials which are easily oxidizable such as copper materials. In this device, as shown in FIG. 4, the heating block 2 is arranged so that it guides the workpieces 1, and an integral lid (that is, a lid consisting of one piece) made of iron is fastened to the heating block 2 itself. Grooves 2a are formed in the upper surface of the heating block 2, and the pipes 6 are installed in these grooves 2a so that the pipes can move upward and downward. The system is arranged so that an inert gas may be introduced and caused to flow over the upper surface of the heating block 2 from the pipes 6.
This device operates as follows: After the pipes 6 are raised so that the workpieces 1 are caused to float above the heating block 2, each workpiece 1 is fed a distance of one pitch by the feeding claws 4. Afterward, the pipes 6 are lowered so that the workpieces 1 rest on the surface of the heating block 2 and the workpieces 1 are thus heated. As a result of the inert gas flowing from the pipes 6, the area above the heating block 2 is filled with an inert gas thus preventing oxidation of the workpieces 1.
The device illustrated in FIG. 5 also prevents oxidation of the workpieces in the same manner as the device illustrated in FIG. 4. Specifically, in this device, an integral lid 5 (that is, a one piece lid) made of iron is fastened to the upper surface of a housing 7 which guides the workpieces 1 so that the lid 5 covers the heating block 2. Holes 2b which allow the flow of insert gas are formed in the heating block 2 parallel to the feeding direction of the workpiece 1. These holes 2b are connected with the upper surface of the heating block 2 by holes 2c. A gas atmosphere is created above the heating block 2 by causing insert gas to flow through the holes 2b from gas supplying ports (not shown). The heating block 2 is arranged so that it can be driven upward and downward. As in the case of the device illustrated in FIG. 3, the heating block 2 is lowered while the workpieces 1 are being fed. After the workpieces 1 have been fed, the heating block 2 is raised, and the workpieces 1 are heated.
It goes without saying that a bonding window is formed in a portion of the lid 5 which corresponds to the position of the bonding tool in the devices shown in FIGS. 4 and 5.
While the above described prior art devices are in general use, they have possess certain disadvantages. In the case of the device shown in FIG. 3 (the open device), since the central portions of the workpieces are exposed, dust and dirt may enter from above and adhere to the workpieces. Such dust and dirt has a deleterious effect on the bonding process.
In the devices shown in FIGS. 4 and 5, since the devices are covered by an iron lid 5, the interior thereof cannot be seen. As a result, observation of oxidation caused discoloration, adjustment of feeding of the workpiece and maintenance of the device are difficult.